Why does the... Torah use the unusual expression "ve'ha'Avanim Tih'yenah al Shemos B'nei Yisrael"?
Seforno: When the donors designate the stones, they should have in mind that the names of the tribes will be inscribed on them, that there must be twelve stones, no more and no less, and that the engraver will engrave the name of the tribe on the stone that is designated for it, and not on another one. 1
As the Pasuk goes on to explain (See Seforno)
Why does the Torah see fit to repeat "Sh'teim-Esrei al Shemosam" (which is seemingly superfluous)?
Oznayim la'Torah: Refer to 28:16:5:1. 1 The Torah therefore clarifies that the names of the twelve tribes must appear on thetwelve stones (one tribe per stone), 2 rather than the Avos apprearing on the first stone, and the tribes on the other eleven.